1. Field of the Invention
The present invention relates to a radiation imaging apparatus, a method of controlling the same, and a radiation imaging system.
2. Description of the Related Art
Recently, medical imaging diagnosis and nondestructive inspection with radiation such as X-rays have been performed by using a radiation imaging apparatus which can output digital images. Japanese Patent Laid-Open No. 2010-268171 proposes a radiation imaging apparatus which automatically determines whether radiation is irradiated from a radiation generating apparatus. This radiation imaging apparatus includes a plurality of pixels. Each pixel includes a conversion element which converts X-rays or light into charge and a switching element which can apply a desired voltage to one of the electrodes of the conversion element. A bias voltage is applied to the other electrode of the conversion element via a bias line. When radiation is irradiated onto the pixel, a current flows in the bias line. By using this, each pixel determines whether radiation is irradiated. The above radiation imaging apparatus resets the voltages applied to the conversion elements by sequentially setting the switching elements of the pixels in a conductive state for each row, thereby transferring the electrical signal based on the dark charge accumulated in each conversion element via the switching element. This sequentially resets the conversion elements. This reset operation causes the current which does not originate from radiation to flow in the bias line. In order to avoid a determination error due to this current, this apparatus performs the above determination upon subtraction of the waveform of this current stored in advance, when actually using a radiation generating apparatus. When the apparatus sequentially and repeatedly resets conversion elements as disclosed in Japanese Patent Laid-Open No. 2010-268171, the current generated by this reset operation changes depending on which row of conversion elements is reset. For this reason, the radiation imaging apparatus disclosed in Japanese Patent Laid-Open No. 2011-185622 is designed to measure, in advance, a profile of currents generated at the time of resetting for all the columns of conversion elements at factory shipment or the like and perform a subtraction process by using the profile.